Methods and apparatuses for use with mode-switchable navigation

ABSTRACT

Methods and apparatuses are provided for use with mode switchable navigation radios and the like. The methods and apparatuses may be implemented to selectively switch between certain operating modes based, at least in part, one or more determinations relating to one or more satellite positioning signals and/or space vehicles.

RELATED APPLICATIONS

This present application is a continuation of U.S. patent applicationSer. No. 13/361,872, entitled “METHODS AND APPARATUSES FOR USE WITHMODE-SWITCHABLE NAVIGATION RADIO,” filed Jan. 30, 2012, which is acontinuation of U.S. patent application Ser. No. 12/400,595, entitled“METHODS AND APPARATUSES FOR USE WITH MODE-SWITCHABLE NAVIGATION RADIO,”filed Mar. 9, 2009, now issued as U.S. Pat. No. 8,106,821, which claimspriority to U.S. Provisional Application No. 61/076,512, entitled“METHODS AND APPARATUSES FOR USE WITH MODE-SWITCHABLE NAVIGATION RADIO,”filed Jun. 27, 2008. The applications recited above are assigned to theassignee hereof and are hereby expressly incorporated by reference intheir entirety herein.

BACKGROUND

1. Field

The subject matter disclosed herein relates to electronic devices and,and more particularly to methods and apparatuses for use in deviceshaving a mode switchable navigation radio.

2. Information

Wireless communication systems are fast becoming one of the mostprevalent technologies in the digital information arena. Satellite andcellular telephone services and other like wireless communicationnetworks may already span the entire globe. Additionally, new wirelesssystems (e.g., networks) of various types and sizes are added each dayto provide connectivity among a plethora of devices, both fixed andportable. Many of these wireless systems are coupled together throughother communication systems and resources to promote even morecommunication and sharing of information. Indeed, it is not uncommon forsome devices to be operatively enabled to communicate with more than onewireless communication system and this trend appears to be growing.

Another popular and increasingly important wireless technology includesnavigation systems and in particular satellite positioning systems (SPS)such as, for example, the global positioning system (GPS) and other likeGlobal Navigation Satellite Systems (GNSS). SPS radios, for example, mayreceive wireless SPS signals that are transmitted by a plurality oforbiting satellites of a GNSS. The SPS signals may, for example, beprocessed to determine a global time, an approximate or accurategeographical location, altitude, and/or speed associated with a devicehaving the SPS radio.

In certain implementations, navigation radios such as an SPS radio maybe implemented to periodically switch ON/OFF at least a portion of itscircuitry, for example, to save power. By way of example, certainnavigation radios may be operatively enabled to switch between a receivemode wherein SPS signals may be acquired and/or tracked, and a sleepmode wherein at least a portion of the radio circuitry may be turned OFF(e.g., powered down in some manner and as such SPS signals may not bereceived in such a sleep mode. The switching between receive (e.g., ON)and sleep (e.g., OFF) modes may occur according to a duty cycle, forexample.

SUMMARY

Methods and apparatuses are provided for use with mode switchablenavigation radios and the like. The methods and apparatuses may beimplemented to selectively switch between certain operating modes based,at least in part, one or more determinations relating to one or moresatellite positioning signals and/or space vehicles.

BRIEF DESCRIPTION OF DRAWINGS

Non-limiting and non-exhaustive aspects are described with reference tothe following figures, wherein like reference numerals refer to likeparts throughout the various figures unless otherwise specified.

FIG. 1 is block diagram illustrating an exemplary environment thatincludes a device having position locating circuitry associated with anavigation radio.

FIG. 2 is an illustrative state diagram showing various exemplary modesin which position locating circuitry within a device, for example, as inFIG. 1, may be operatively enabled to operate.

FIG. 3 is a block diagram illustrating certain features of an exemplarydevice that may, for example, be implemented in the environment of FIG.1.

FIG. 4 is a flow diagram illustrating a method that may, for example, beimplemented in an exemplary device that may, for example, be implementedin the environment of FIG. 1.

DETAILED DESCRIPTION

Methods and apparatuses are provided for use with mode switchablenavigation radios and the like. The methods and apparatuses may beimplemented to selectively switch between certain operating modes based,at least in part, a mode-switching test that takes into considerationone or more non-timed test conditions to determine whethermode-switching may be enabled.

In certain exemplary implementations, such a mode-switching test maysupport dynamic optimization for switching at least a portion ofposition location circuitry within a navigation radio from a first modeto a second mode wherein if operating in the second mode the navigationradio may consume less electrical power. Such mode-switching test may,for example, consider certain non-timed test conditions that may beindicative the navigation radio's ability to maintain or otherwisesupport a desired level of position location service/accuracy and/orattempt to meet other desired performance metrics.

By way of example but not limitation, such a first mode may beassociated with a receive mode having essentially a 100% duty cycle(e.g., substantially always ON), and a second mode may be associatedwith a receive mode having less than a 100% duty cycle (e.g., possiblyswitching between ON and OFF).

In other example implementations, such first and second modes maytogether be associated with a given duty cycle, such that the first modemay be associated with an ON operation and the second mode may beassociated with an OFF operation.

Such mode-switching, if enabled, may selectively switch back from thesecond mode to the first mode based, at least in part, on the occurrenceof a mode switching event, such as, for example, a timed conditions (atimer, duty cycle, etc.), which may be predetermined, or varied and/orotherwise dynamically established based on one or more of non-timed testconditions and/or other operative or performance based factors.

In accordance with one aspect, an apparatus may be provided whichincludes position locating circuitry and a controller. The positionlocating circuitry may be operatively enabled to acquire wirelesssignals associated with a satellite positioning system (SPS) ifoperating in a first mode. The position locating circuitry may beoperatively enabled to at least maintain local clock information and tonot acquire the wireless signals at all or at certain times if operatingin a second mode. In certain implementations, the local clockinformation may be or may have been previously substantially calibratedwith a clock associated with an SPS clock signal (e.g., from a phaselock loop (PLL) circuit or other like within the radio).

The controller may, for example, be operatively enabled to selectivelyswitch the position locating circuitry from the first mode to the secondmode based, at least in part, on at least one mode-switching test beingsatisfied. The mode-switching test may be based, at least in part, on atleast one non-timed test condition.

By way of example but not limitation, such non-timed test conditions mayinclude one or more of: a first test condition wherein wireless signalsof at least a first threshold signal strength have been acquired from afirst set of space vehicles (SVs); a second test condition whereinwireless signals of at least the first threshold signal strength havebeen acquired from at least a first threshold number of SVs; a thirdtest condition wherein wireless signals of at least a second thresholdsignal strength have been acquired from at least a second thresholdnumber of SVs; a fourth test condition wherein SV position informationis accessible for at least the first set of SVs; a fifth test conditionwherein no additional SV position information is currently beingreceived for any of the first set of SVs; a sixth test condition whereinno SVs are being acquired; a seventh test condition wherein an errorassociated with a current position location as determined based, atleast in part, on at least a portion of the wireless signals associatedwith the SPS does not exceed a position location error threshold; aneighth test condition wherein the position locating circuitry iscurrently operating in the first mode; and/or a ninth test conditionwherein Satellite Health information is not currently being received forany of the SVs. By way of example but not limitation, such non-timedtest conditions may also and/or alternatively be combined in variousmanners.

In certain implementations, such non-timed test conditions may becombined to form a mode-switching test. For example, at least a firstportion of a mode-switching test may be satisfied if the first testcondition, and the seventh test condition and the eighth test conditionand at least one or more of the fourth test condition and/or the fifthtest condition are determined by the controller to be TRUE. For example,another mode-switching test may be satisfied if such a first portion ofthe mode-switching test is satisfied and if at least one of both thesecond test condition and the sixth test condition are determined by thecontroller to be TRUE and/or the third test condition is determined bythe controller to be TRUE.

The second mode may include, for example, a reduced power mode in whichat least a portion of the position locating circuitry operativelyenabled to acquire the wireless signals may be turned OFF and/orotherwise deactivated in some manner at all times or at certain times.Hence, a second mode may have a duty cycle that may be 0% (e.g., neverON) or less than 100% (e.g., sometimes but not always ON).

The apparatus may also be enabled to operate in other modes and/ormodified first modes that may prevent switching from a first mode to asecond mode. By way of example but not limitation, a modified first modemay include at least one of an emergency service mode, an assistedservice mode, an extended receiver ON mode, an initializing mode, adevice power charging mode, a device communicating mode, and/or adetected device movement mode.

The controller may also be operatively enabled to selectively switch theposition locating circuitry from the second mode back to the first modebased, at least in part, on an occurrence of a mode-switching event. Forexample, a mode-switching event may be associated with a timed periodand/or associated with the mode-switching test no longer beingsatisfied.

In accordance with another aspect, an exemplary method may include, withposition locating circuitry operating in a first mode, acquiringwireless signals associated with a satellite positioning system (SPS).The method may also include selectively switching the position locatingcircuitry from a first mode to a second mode based, at least in part, onat least one mode-switching test being satisfied, wherein themode-switching test may be based, at least in part, on at least onenon-timed test condition. The method may further include, with theposition locating circuitry operating in the second mode, maintaininglocal clock information substantially calibrated with a clock associatedwith the SPS and either not acquiring wireless signals or acquiringwireless signals less often than during a first mode. In certainimplementations the method may also include selectively switching theposition locating circuitry from the second mode to the first modebased, at least in part, on an occurrence of a mode-switching event.

In accordance with yet another aspect, an apparatus may be implementedwhich may include a radio for acquiring wireless signals associated witha SPS if the apparatus is operating in a first mode, circuitry formaintaining local clock information substantially calibrated with aclock associated with the SPS while not acquiring the wireless signalsif the apparatus may be operating in a second mode, and a controller forselectively switching an operation of the apparatus from the first modeto the second mode based, at least in part, on at least onemode-switching test being satisfied, wherein the mode-switching test maybe based, at least in part, on at least one non-timed test condition.

In accordance with still other aspects, an article may be provided withincludes a computer readable medium having computer implementableinstructions stored thereon. The instructions, if implemented by one ormore processing units, may adapt the one or more processing units todetermine if at least one mode-switching test may be satisfied, the atleast one mode-switching test being based, at least in part, on at leastone non-timed test condition. In response to the mode-switching testbeing determined as being satisfied, the one or more processing unitsmay selectively switch position locating circuitry operating in a firstmode in which wireless signals associated with a satellite positioningsystem (SPS) may be acquired to a second mode wherein local clockinformation substantially calibrated with a clock associated with theSPS is maintained but the wireless signals are either not being acquiredor are acquired less often than during a first mode.

FIG. 1 is a block diagram illustrating a wireless environment 100 thatmay include various computing and communication resources operativelyenabled to provide navigation services and possibly other communicationservices in accordance with certain exemplary implementations of presentdescription.

Wireless environment 100 may be representative of any system(s) or aportion thereof that may include at least one device 102 operativelyenabled to at least receive wireless signals associated with at leastone navigation system 106 (e.g., a satellite positioning system (SPS,and/or the like). Device 102, as illustrated in this example, may alsobe operatively enabled to send/receive signals with at least onewireless system 104.

Device 102 may, for example, include a mobile device or a device thatwhile movable may be primarily intended to remain stationary. Thus, asused herein, the terms “device” and “mobile device” may be usedinterchangeable as each term is intended to refer to any single deviceor any combinable group of devices that may transmit and/or receivewireless signals. The terms “receive” and “acquire” are usedinterchangeably herein and are both intended to represent the receptionof a wireless signal such that information that is carried via thewireless signal may be operatively acquired by the receiving device.

With this in mind and by way of example but not limitation, asillustrated using icons in FIG. 1, device 102 may include a mobiledevice such as a cellular phone, a smart phone, a personal digitalassistant, a portable computing device, and/or the like or anycombination thereof. In other exemplary implementations, device 102 maytake the form of a machine that is mobile or stationary. In still otherexemplary implementations, device 102 may take the form of one or moreintegrated circuits, circuit boards, and/or the like that may beoperatively enabled for use in another device.

Regardless of the form of device 102, device 102 may include at leastone navigation radio 112 of which at least a portion may be enabled tooperate according to two or more modes of operation. The term “radio” asused herein refers to any circuitry and/or the like that may beoperatively enabled to at least receive wireless signal. In certainimplementations a radio may also be operatively enabled to transmitwireless signals. In certain implementations, device 102 may include twoor more radios. Such radios may, for example, be operatively enabled toshare a portion of circuitry and/or the like (e.g., a processing unit,memory, antenna, power supply, etc.).

By way of example but not limitation, in some of the examples presentedherein device 102 may include a first radio that is operatively enabledto receive wireless signals associated with at least one navigationsystem 106 and a second radio that is operatively enabled to receive andtransmit wireless signals associated with at least one wireless system104. Wireless system 104 may include, for example, a wirelesscommunication system, such as, e.g., a wireless telephone system, awireless local area network, and/or the like. Wireless system 104 mayinclude, for example, a wireless broadcast system, such as, e.g., atelevision broadcast system, a radio broadcast system, and/or the like.In certain implementations, device 102 may be operatively enabled onlyto receive wireless signals from wireless system 104, while in otherimplementations mobile station 102 may be operatively enabled only totransmit wireless signals to wireless system.

As illustrated in FIG. 1, wireless system 104 may be operatively enabledto communicate with and/or otherwise operatively access other devicesand/or resources as represented simply by cloud 110. For example, cloud110 may include one or more communication devices, systems, networks, orservices, and/or one or more computing devices, systems, networks, theInternet, various computing and/or communication services, and/or thelike, or any combination thereof.

Wireless system 104 may, for example, be representative of any wirelesscommunication system or network that may be operatively enabled toreceive and/or transmit wireless signals. By way of example but notlimitation, wireless system 104 may include a wireless wide area network(WWAN), a wireless local area network (WLAN), a wireless personal areanetwork (WPAN), a wireless metropolitan area network (WMAN), a Bluetoothcommunication system, WiFi communication system, Global System forMobile communications (GSM) system, Evolution Data Only/Evolution DataOptimized (EVDO) communication system, Ultra Mobile Broadband (UMB)communication system, Long Term Evolution (LTE) communication system,Mobile Satellite Service-Ancillary Terrestrial Component (MSS-ATC)communication system, and/or the like.

The term “network” and “system” may be used interchangeably herein. AWWAN may be a Code Division Multiple Access (CDMA) network, a TimeDivision Multiple Access (TDMA) network, a Frequency Division MultipleAccess (FDMA) network, an Orthogonal Frequency Division Multiple Access(OFDMA) network, a Single-Carrier Frequency Division Multiple Access(SC-FDMA) network, and so on. A CDMA network may implement one or moreradio access technologies (RATs) such as cdma2000, Wideband-CDMA(W-CDMA), to name just a few radio technologies. Here, cdma2000 mayinclude technologies implemented according to IS-95, IS-2000, and IS-856standards. A TDMA network may implement Global System for MobileCommunications (GSM), Digital Advanced Mobile Phone System (D-AMPS), orsome other RAT. GSM and W-CDMA are described in documents from aconsortium named “3rd Generation Partnership Project” (3GPP). Cdma2000is described in documents from a consortium named “3rd GenerationPartnership Project 2” (3GPP2). 3GPP and 3GPP2 documents are publiclyavailable. A WLAN may include an IEEE 802.11x network, and a WPAN mayinclude a Bluetooth network, an IEEE 802.15x, for example. Such locationdetermination techniques described herein may also be used for anycombination of WWAN, WLAN, WPAN, WMAN, and/or the like.

Wireless system 104 may, for example, be representative of any wirelessbroadcast system that may be operatively enabled to at least receivewireless signals. By way of example but not limitation, a wirelessbroadcast system may include a MediaFLO system, a Digital TV system, aDigital Radio system, a Digital Video Broadcasting-Handheld (DVB-H)system, a Digital Multimedia Broadcasting (DMB) system, an IntegratedServices Digital Broadcasting-Terrestrial (ISDB-T) system, and/or otherlike systems and/or related broadcast techniques.

Device 102 may be operatively enabled to at least receive wirelesssignals from at least one navigation system 106 which is illustrated inFIG. 1 as a satellite positioning system (SPS) having a plurality of SPSsignal transmitting satellites 106-1, 106-2, 106-3, . . . , 106-x.Indeed, in certain example implementations, device 102 may only beconfigured to receive wireless signals, such as, SPS signals. Here, forexample, device 102 may include a personal navigation device (PND),personal navigation assistant (PNA), and/or the like. In other exampleimplementations, device 102 may also communicate with other devices viawired and/or wireless transmitted signals. Here, for example asillustrated in FIG. 1, device 102 may transmit signals to wirelesssystem 104. Those skilled in the art will recognize that navigationsystem 106 may include additional transmitting and/or other supportingresources in addition to or instead of the satellites as illustrated.

In certain implementations, navigation system 106 may be operativelyenabled to provide other non-navigation related services (e.g.,communication services, or the like). As such, in certainimplementations device 102 may be operatively enabled to transmitwireless signals to navigation system 106.

The space vehicles (SVs) of navigation system 106 may be operativelyenabled to transmit a unique wireless signal (SPS signal) of which, atleast a portion, may be received by device 102 and used in some mannerfor navigation, for example, to determine a time, a range, a location, aposition, etc. The specific navigation signaling and locationdetermining techniques may vary depending on the navigation system(s)being used. Such SVs may be operatively enabled to transmit one or moresignals at the same or different carrier frequencies. For example, a GPSsatellite may be operatively enabled to transmit L1 C/A and L1C signalsin the same band, as well as, the L2C and L5 signals at other carrierfrequencies, etc. Furthermore, such SPS signals may include encryptedsignals.

A SPS typically includes a system of transmitters positioned to enableentities to determine their location on or above the Earth based, atleast in part, on signals received from the transmitters. Such atransmitter typically transmits a signal marked with a repeatingpseudo-random noise (PN) code of a set number of chips and may belocated on ground based control stations, user equipment and/or spacevehicles. In a particular example, such transmitters may be located onEarth orbiting SVs. For example, a SV in a constellation of GlobalNavigation Satellite System (GNSS) such as Global Positioning System(GPS), Galileo, Glonass or Compass may transmit a signal marked with aPN code that is distinguishable from PN codes transmitted by other SVsin the constellation. In accordance with certain aspects, the techniquespresented herein are not restricted to global systems (e.g., GNSS) forSPS. For example, the techniques provided herein may be applied to orotherwise operatively enabled for use in various regional systems, suchas, e.g., Quasi-Zenith Satellite System (QZSS) over Japan, IndianRegional Navigational Satellite System (IRNSS) over India, Beidou overChina, etc., and/or various augmentation systems (e.g., an SatelliteBased Augmentation System (SBAS)) that may be associated with orotherwise operatively enabled for use with one or more global and/orregional navigation satellite systems. By way of example but notlimitation, an SBAS may include an augmentation system(s) that provideintegrity information, differential corrections, etc., such as, e.g.,Wide Area Augmentation System (WAAS), European Geostationary NavigationOverlay Service (EGNOS), Multi-functional Satellite Augmentation System(MSAS), GPS Aided Geo Augmented Navigation or GPS and Geo AugmentedNavigation system (GAGAN), and/or the like. Such SBAS may, for example,transmit SPS and/or SPS-like signals that may also be interfered with bycertain wireless communication signals, etc. Thus, as used herein an SPSmay include any combination of one or more global and/or regionalnavigation satellite systems and/or augmentation systems, and SPSsignals may include SPS, SPS-like, and/or other signals associated withsuch one or more SPS.

To estimate its location, device 102 may determine pseudorangemeasurements to SVs that are “in view” of its receiving radio using wellknown techniques based, at least in part, on detections of PN codes insignals received from the SVs. Such a pseudorange to a SV may bedetermined based, at least in part, on a code phase detected in areceived signal marked with a PN code associated with the SV during aprocess of acquiring the received signal at the receiving radio. Toacquire the received signal, device 102 may, for example, be operativelyenabled to correlate the received signal with a locally generated PNcode associated with a SV. For example, device 102 may correlate such areceived signal with multiple code and/or time shifted versions of sucha locally generated PN code. Detection of a particular time and/or codeshifted version yielding a correlation result with the highest signalpower may indicate a code phase associated with the acquired signal foruse in measuring pseudorange as discussed above.

Thus, in certain implementations, device 102 may be operatively enabledto determine its location in such a manner or other like manner withoutadditional support from other devices. In other implementations,however, device 102 may be enabled to operate in some manner with one ormore other devices to determine its location and/or to support othernavigation related operations. Such navigation techniques are wellknown.

In certain implementations, device 102 may be operatively enabled toreceive SPS signals from one or more GNSS, such as, for example, GPS,Galileo, GLONASS, Compass, or other like system that uses a combinationof these systems, or any SPS developed in the future, each referred togenerally herein as a SPS. As used herein, an SPS will also beunderstood to include pseudolite systems.

Pseudolites are ground-based transmitters that broadcast a PN code orother ranging code (similar to a GPS or CDMA cellular signal) modulatedon an L-band (or other frequency) carrier signal, which may besynchronized with GPS time. Each such transmitter may be assigned aunique PN code so as to permit identification by a remote receiver.Pseudolites may be useful in situations where signals from an orbitingSV might be unavailable, such as in tunnels, mines, buildings, urbancanyons or other enclosed areas. Another implementation of pseudolitesis known as radio-beacons. The terms “satellite” and “SV”, as usedherein, are interchangeable and intended to include pseudolites,equivalents of pseudolites, and possibly others. The term “SPS signals”,as used herein, is intended to include SPS-like signals from pseudolitesor equivalents of pseudolites.

Reference is now made to FIG. 2, which is a state diagram illustratingcertain exemplary operating mode environment 200 that device 102 may beselectively operatively enabled to implement with regard to at least aportion of radio 112. Here, for example, operating mode environment 200may be implemented to allow device 102 and/or at least a portion ofradio 112 to selectively operate in at least a first mode 202 or asecond mode 204.

In certain example implementations, first mode 202 may operatively adaptdevice 102 and/or at least a portion of radio 112 to receive and acquireSPS signals in support of various search operations, verificationoperations, tracking operations, and/or the like. Such a first mode 202may, for example, require various circuitries within device 102 and/orat least a portion of radio 112 to be turned ON and operating in somemanner. For example, an RF front-end circuit and/or signal processorcircuitry may be functioning to receive and acquire one or more SPSsignals. First mode 202 may, for example, be associated with a dutycycle that may be 100% (e.g., substantially always ON).

Device 102 and/or at least a portion of radio 112 may, for example, beoperatively enabled to transition per transition action 210 from firstmode 202 to second mode 204. Various techniques are presented insubsequent sections illustrating certain exemplary tests and/orconditions that may be considered by controlling logic or the like toinitiate transition action 210.

In certain example implementations, second mode 204 may adapt at least aportion of radio 112 to reduce power consumption by turning OFF orotherwise affecting the operation of all or part of the circuitryassociated with receiving, acquiring, and/or otherwise processing SPSsignals. For example, all or part of an RF front-end circuit and/or allor part of signal processor circuitry may be turned OFF (e.g., powereddown, disabled, or otherwise altered) such that device 102 no longerreceives and/or acquires SPS signals. Thus, second mode 204 may, forexample, be associated with a duty cycle that may be 0% (e.g., never ON)or less than 100% (e.g., not always ON). By way of example but notlimitation, second mode 204 may be associated with a duty cycle of 20%for a period of time (e.g., one second) such that device 102 and/or atleast a portion of radio 112 may remain OFF for 80% of the period oftime (e.g., 800 milliseconds) and ON for 20% of the period of time(e.g., 200 milliseconds).

In certain example implementations, device 102 and/or at least a portionof radio 112 may maintain or otherwise establish local clockinformation/signal or other like timing information/signal that may becalibrated with or otherwise associated in some manner with an SPS clockinformation/signal associated with an SPS. Such techniques and localclock circuitry are known.

Device 102 and/or at least a portion of radio 112 may, for example, beoperatively enabled to transition per transition action 212 from secondmode 204 to first mode 202. Various techniques are presented insubsequent sections illustrating certain exemplary tests and/orconditions that may be considered by controlling logic or the like toinitiate transition action 212.

In certain exemplary implementations, transition action 212 mayselectively switch device 102 and/or at least a portion of radio 112back from the second mode to the first mode based, at least in part, ona timed condition 380 (see, FIG. 3, e.g., a timer, duty cycle, etc.)and/or other like mode-switching events. In certain exemplaryimplementations, timed condition 380 may be established and/or otherwiseadjusted dynamically based, at least in part, on mode-switching test 320and/or one more non-timed test conditions 322 and/or informationassociated therewith. Here, for example, processing unit 304 may beoperatively enabled to establish timed condition 380.

To the contrary, rather than automatically transitioning from first mode202 to second mode 204 based on a timed condition, controller 302 may beoperatively enabled per the techniques herein to determine/verify thatmode-switching test 320 is satisfied prior to initiating transition 210.

Also illustrated in FIG. 2 are some additional (optional) modes, whichmay be functionally implemented within first mode 202 (e.g., modifyingin some manner first mode 202) and/or as functionally separate modes. Inthis illustration, for example, a third mode 206 and a fourth mode 208are shown as separate modes of operation. It should be clear thatclaimed subject matter is not intended to be limited by these examples.

As shown, device 102 and/or at least a portion of radio 112 may, forexample, be operatively enabled to transition from first mode 202 toeither third mode 206 or fourth mode 208. Device 102 and/or at least aportion of radio 112 may, for example, also be operatively enabled totransition between third mode 206 and fourth mode 208. As described ingreater detail below, in certain exemplary implementations, device 102and/or at least a portion of radio 112 may be operatively enabled toprevent a transition (switch) from first mode 202 to second mode 204 ifoperating in either third or fourth modes, and/or similar modified firstmode.

In other words, third and/or fourth modes may be implemented which actto prevent one or more of transition 210 and/or transition action 212from occurring. For example, third and/or fourth modes may beimplemented to prevent one or more of transition 210 and/or transitionaction 212 from occurring so as to receive Health Information from anSV. For example, GPS/GNSS Health information may be transmitted forabout 12 seconds in every 750 second period. Thus, device 102 may beenabled to keep track of SPS time and switch to a third or fourth modeif it is determined that such Health Information may soon be received.

In another example, third and/or fourth modes may be implemented toprevent one or more of transition 210 and/or transition action 212 fromoccurring so as to allow reception and/or decoding of orbital data(Ephemeris) before the data expires, and/or as otherwise needed. Here,for example, such reception and/or decoding may occur roughly every 2, 4or 6 hours (e.g., depending on the SV orbital parameters, data accuracy,data age, etc.) and a random time slot may be chosen before 30 minutesof expiry to decode the data. In this manner, device 102 may be enabledto continue to operate and generate periodic position fixes throughorbital data changes.

By way of further example but not limitation, third and/or fourth modesmay be operatively enabled to support certain navigation relatedoperations that may be adversely affected should the mode/operations beinterrupted. For example, third mode 206 may include at least one of anemergency service mode operation, an assisted service mode operation, anextended receiver-ON mode operation, an initializing mode operation,and/or the like.

By way of example but not limitation, third and/or fourth modes may beoperatively enabled to support certain device related operations thatmay be adversely affected should the mode/operations be interrupted. Forexample, fourth mode 208 may include at least one of a device powercharging mode operation, a device communicating mode operation, adetected device movement mode operation, and/or the like.

Reference is now made to FIG. 3, which is a block diagram is depictingan exemplary system 300 that may be operatively enabled for use inenvironment 100.

As shown, device 102 may include a controller 302 that may be coupled toposition locating circuitry 308. Controller 302 or portions there of maybe part of radio 112. Controller 302 may, for example, include one ormore processing units 304. Controller 302 may include and/or otherwiseoperatively access memory 306. Controller 302 may, for example, includeand/or otherwise operatively access a computer readable medium 360having computer implementable instructions 362 and/or other likeinformation/data stored thereon. In certain implementations, controller302 may include all or a portion of local clock circuitry 332.

Position locating circuitry 308 or portions there of may be part ofradio 112. Position locating circuitry may, for example, be operativelyenabled to acquire SPS signal 310 transmitted by SPS 106. Positionlocating circuitry may, for example, include a mode-switching portion312. All or part of mode-switching portion 312 may, for example, beoperatively enabled to turn OFF/ON or otherwise alter its functionbased, at least in part, on transition action 210 and/or transitionaction 212, respectively. Mode-switching portion 312 may, for example,include at least one receiver having RF front-end circuitry 314, signalprocessor circuitry 316, etc. Position locating circuitry 308 may, forexample, include all or portions of local clock circuitry 332, which maybe calibrated with or otherwise associated with SPS clock 334. SPS clock334 may be received and/or derived from SPS signal 310, for example.

As shown in this example, memory 306 may include or otherwise beoperatively enabled to store and provide instructions and/or informationrelating at least one of the first mode 202, second mode 204, third mode206 (optional), and/or fourth mode 208 (optional).

Memory 306 may include or otherwise be operatively enabled to store andprovide instructions and/or information relating to at least onemode-switching test 320, which may be performed by processing unit 304to determine if a particular transition action 210/212 may be providedor otherwise applied to position locating circuitry 308.

Mode-switching test 320 may, for example, be operatively enabled toconsider one or more test conditions 322. In certain example,implementations to initiate a transition action 210 (e.g., a switch fromfirst mode 202 to second mode 204) one or more non-timed test conditionsmay be considered and/or combined as part of mode-switching test 320. Byway of example but not limitation, such non-timed test conditions 322may include: a first test condition 322-1, wherein wireless signals ofat least a first threshold signal strength have been acquired from afirst set of space vehicles (SVs); a second test condition 322-2 whereinwireless signals of at least the first threshold signal strength havebeen acquired from at least a first threshold number of SVs; a thirdtest condition 322-3 wherein wireless signals of at least a secondthreshold signal strength have been acquired from at least a secondthreshold number of SVs; a fourth test condition 322-4 wherein SVposition information is accessible for at least the first set of SVs; afifth test condition 322-5 wherein no additional SV position informationis currently being received for any of the first set of SVs; a sixthtest condition 322-6 wherein no SVs are being acquired; a seventh testcondition 322-7 wherein an error associated with a current positionlocation as determined based, at least in part, on at least a portion ofthe wireless signals associated with the SPS does not exceed a positionlocation error threshold; an eighth test condition 322-8 wherein theposition locating circuitry is currently operating in the first mode;and/or a ninth test condition 322-9 wherein Satellite Health informationis not currently being received for any of the SVs.

For example, at least a first portion of mode-switching test 320 may besatisfied if the first test condition 322-1, and the seventh testcondition 322-7 and the eighth test condition 322-8 and at least one ormore of the fourth test condition 322-4 and/or the fifth test condition322-5 are determined by controller 302 to be TRUE. For example, anothermode-switching test may be satisfied if such a first portion of themode-switching test is satisfied and if at least one of both the secondtest condition 322-2 and the sixth test condition 322-6 are determinedby the controller to be TRUE and/or the third test condition 322-3 isdetermined by controller 302 to be TRUE. Some additional examples forsuch tests, test conditions, and/or combinatorial decision processes arepresented in subsequent sections.

As shown in the example implementation of FIG. 3, to support themode-switching test 320 and/or certain test conditions 322, memory 306may also include further SV position information 324, position locationinformation 326, position location error information 328, and/or one ormore threshold values 330.

Device 102 may include a communication interface 350 which may beoperatively enabled to connect device 102 to network 104 and/or otherlike resources. As shown in this example, communication interface 350may include a transceiver 352 and/or the like to support wired and/orwireless communications. Here, in certain implementations, one or moretest conditions 322 may be associated with the status of communicationinterface 350. For example, communication interface may be implementedto support an operation associated with third 206 and/or fourth mode 208that may lead to a mode-switching test failure, which may prohibitinitiating transition action 210 and/or lead to the initiation oftransition action 212.

Device 102 may include a user interface 338 which may be operativelyenabled to at least receive user inputs. For example, user inputs may bereceived through a keypad, keyboard, mouse, button, microphone, camera,etc. In certain implementations, one or more test conditions 322 may beassociated with a user input. For example, a user input may initiate anoperation associated with third 206 and/or fourth mode 208 that may leadto a mode-switching test failure, which may prohibit initiatingtransition action 210 and/or lead to the initiation of transition action212.

Device 102 may include a motion detector 344 which may be operativelyenabled to determine whether device 102 may be moving and/or may bestationary. For example, motion detector 344 may include anaccelerometer, gyroscope, etc. In certain implementations, one or moretest conditions 322 may be associated with such motion detection. Forexample, detected movement and/or a stationary status may initiate anoperation associated with third 206 and/or fourth mode 208 that may leadto a mode-switching test failure, which may prohibit initiatingtransition action 210 and/or lead to the initiation of transition action212.

Device 102 may include a power supply 340 which may be operativelyenabled to connect to an external power source 342. For example, powersupply 340 may include one or more rechargeable batteries or the like,and power source 342 may include a corresponding charger/adapter. Incertain implementations, one or more test conditions 322 may beassociated with such connections/charging/power status. For example, ifdevice 102 is connected to power source 342 an operation associated withthird 206 and/or fourth mode 208 that may lead to a mode-switching testfailure, which may prohibit initiating transition action 210 and/or leadto the initiation of transition action 212.

Reference is now made to FIG. 4, which is a flow diagram illustrating anexemplary method 400 that may, for example, be implemented in device 102and/or the like.

At block 402, device 102 and/or a portion thereof may be operativelyenabled to operate in a first mode to acquire wireless SPS signals.

At block 404, device 102 and/or a portion thereof may be operativelyenabled to switch from the first mode to a second mode based, at leastin part, on at least one mode-switching test being satisfied. Suchmode-switching test may be based, at least in part, on at least onenon-timed test condition.

At block 406, device 102 and/or a portion thereof may be operativelyenabled to operate in the second mode while maintaining local clockinformation that may be substantially calibrated with a clock associatedwith the SPS and while either not acquiring wireless signals oracquiring wireless signals less often than during the first mode.

At block 408, device 102 and/or a portion thereof may be operativelyenabled to switch from the second mode to the first mode based, at leastin part, on an occurrence of a mode-switching event (e.g., transitionaction 212).

Some example mode-switching tests and test conditions will now bepresented that may be implemented in device 102 for use with SPS 106including GPS. These are but a few examples and as such are not intendedto limit claimed subject matter.

In certain implementations, of device 102, power consumption is animportant performance consideration. The techniques provided herein maybe operatively enabled to allow certain devices to operate with reducedbattery usage without significantly compromising on performance in termsof accuracy and/or response times.

As described herein, certain modes themselves and/or by selectivelyswitching between certain modes may reduce the power consumption byturning selected portions of RF related circuitry and/or otherassociated hardware ON and OFF. Thus, for example, one or more modes maybe selectively enabled as needed to decode or not to decode navigation.

As described below, the techniques herein may perform particularly wellif the wireless SPS signals 310 are strong enough to be observed withina specified period. As mentioned, one potential benefit of suchmode-switching techniques may be a reduction in power consumptionwithout significantly affecting position location fix times and/oraccuracy. However, in certain situations there may be a slightdegradation in performance since SV signals are not acquired very often(e.g., not acquired while device 102 may be OFF as part of second mode204). In certain implementations, code phase measurements may be noisierthan those that may be obtained from extended acquisition operations(e.g., remaining in first mode 202, third mode 206, and/or possiblyfourth mode 208). Moreover, carrier phase measurements may not beobtained since data-decoding may not be continuous.

Another potential affect of such mode-switching techniques may be thatSV signals may not be acquired due to a limited duration with an RF ONperiod. For example, SV signals may not be acquired if a searchoperation coincides with an RF ON period. Thus, such affects may placeadditional test conditions on such mode-switching. For example, a testcondition may be established such that mode transition 210 may occur ifthere are no unknown SVs and/or the search strategy is not engaged in aninitial SV search.

In certain example implementations, there may be a chance that thesearch space exceeds a search capacity. However, an exception may occur,for example, if there are enough signals from SVs, which have been foundto be strong, mode-switching may proceed if an accurate enough positionfix may be determined. For example, in certain implementations acondition test may be established such that mode transition 210 mayoccur if at least six GPS SVs have strong enough signals (e.g., at least35 dB-Hz). Here, the signals may be used to give some margin to isolatefaulty measurements if possible. Thus, for example, in certainimplementations, mode transition 210 may occur if all applicable GPS SVsare in a dedicated track, and/or at least six of the GPS SVs that are ina dedicated track have signals of at least 35 dB-Hz.

The examples above and also those below may provide non-timed testconditions that may be considered in determining as part of amode-switching test if a mode transition 210 may occur.

For example, first test condition 322-1, wherein wireless signals of atleast a first threshold signal strength have been acquired from a firstset of SVs, may be operatively enabled for an exemplary GPSimplementation such that all applicable SVs with CN_(o)>24 dB-Hz haveGPS Time set (e.g., the CodePhase, BitPhase and Integer Millisecond isknown for each SV).

For example, second test condition 322-2 wherein wireless signals of atleast the first threshold signal strength have been acquired from atleast a first threshold number of SVs may be operatively enabled for anexemplary GPS implementation such that there are at least four strongenough SVs (e.g., with CN_(o)>24 dB-Hz). Thus, by way of example but notlimitation, a first threshold number of SVs may be four, and a firstthreshold signal strength may be at least 24 dB-Hz. In otherimplementations, a first threshold number of SVs may be less than orgreater than four, and/or a first threshold signal strength may be lessthan or greater than 24 dB-Hz. For example, in certain implementations,the first threshold signal strength may be between 24 dB-Hz and 30 dB-Hzand/or the first threshold number of SVs may be between three and five.

For example, third test condition 322-3 wherein wireless signals of atleast a second threshold signal strength have been acquired from atleast a second threshold number of SVs may be operatively enabled for anexemplary GPS implementation such that at least six SVs in dedicatedtracking are strong enough (e.g., with CN_(o)>35 dB-Hz). Thus, by way ofexample but not limitation, a second threshold number of SVs may be six,and a second threshold signal strength may be at least 35 dB-Hz. Inother implementations, a second threshold number of SVs may be less thanor greater than six, and/or a second threshold signal strength may beless than or greater than 35 dB-Hz. For example, in certainimplementations, second threshold number of SVs may be between five andeight, and/or second threshold signal strength may be between 35 dB-Hzand 40 dB-Hz.

For example, fourth test condition 322-4 wherein SV position informationis accessible for at least the first set of SVs may be operativelyenabled for an exemplary GPS implementation such that Ephemeris and/orpredictive orbital model information (e.g., XTRA Almanac Corrections,etc.) for all applicable SVs with CN_(o)>24 dB-Hz is known. Thus, by wayof example but not limitation, a first set of SVs may be identified ashaving a signal strength of a particular strength. In otherimplementations, a first set of SVs may be identified in other manners,e.g., a set number, availability, applicability, range, direction,angle, etc.

As used herein, “SV position information” may include correctioninformation associated with at least one satellite in should be in view.By way of example but not limitation, such correction information mayinclude either orbital information derived from ephemeris and/or somesimilar data transmitted by the SVs and/or orbital information derivedfrom predictive methods. In certain example implementations, correctioninformation may include, for example, Ephemeris information that may betransmitted with a validity period of + or −2 hours from the TOE (timeof ephemeris).

For example, fifth test condition 322-5 wherein no additional SVposition information is currently being received for any of the firstset of SVs may be operatively enabled for an exemplary GPSimplementation such that if sub-frames 4 and 5 are being transmittedthen there may be no need to receive and decode such because suchEphemeris (EPH) information may be transmitted in first 3 sub-frames.

For example, sixth test condition 322-6, wherein no SVs are beingacquired, may be operatively enabled for an exemplary GPS implementationsuch that there may be no applicable SVs in a search list(s), e.g., allapplicable SVs may be being subjected to one or more dedicated trackingoperation(s) and/or the like.

For example, seventh test condition 322-7 wherein an error associatedwith a current position location as determined based, at least in part,on at least a portion of the wireless signals associated with the SPSdoes not exceed a position location error threshold may be operativelyenabled for an exemplary GPS implementation such that the horizontalestimated position error (HEPE) or the like of the most recent computedposition fix may be less than 50 meters. Thus, by way of example but notlimitation, a position location error threshold may be 50 meters. Inother implementations, a position location error threshold may be lessthan or greater than 50 meters. For example, the position location errorthreshold may include a threshold HEPE be between 30 meters and 100meters.

For example, eighth test condition 322-8 wherein the position locatingcircuitry is currently operating in the first mode may be operativelyenabled for an exemplary GPS implementation such that the navigationradio may be determined to not be in an extended receiver ON mode (e.g.,not trying to decode EPH). For example, eighth test condition 322-8wherein the position locating circuitry is currently operating in thefirst mode may be operatively enabled for an exemplary GPSimplementation such that the device may not be supporting an E911scenario (e.g., control plane (CP) UE assisted, CP UE based, and CPMS-assisted E911), and/or an MS-Assisted/UE-assisted scenario (e.g., forE911, or the like wherein accuracy and timing, and call may be moreimportant than saving power). Additionally, eighth test condition 322-8may also consider if any other modes and/or operations, such as, e.g.,those presented herein with regard to third mode 206 and/or fourth mode208.

For example, ninth test condition 322-9 wherein Satellite Healthinformation is not currently being received for any of the SVs.

Two or more of the example test conditions 322 above may be combined incertain implementations. By way of example, first test condition 322-1and second test condition 322-2 may be combined to produce a first testcondition 322-1′ (not shown) wherein, for example, wireless signals ofat least a first threshold signal strength have been acquired from atleast a first threshold number of SVs. In other example implementations,first test condition 322-1 may be combined with fourth test condition322-4 and/or fifth test condition 322-5 to indicate that SV signalstrength may be sufficient but that applicable Ephemeris information maybe unavailable and/or new Ephemeris information may be beingtransmitted.

The methodologies described herein may be implemented by various meansdepending upon the application. For example, these methodologies may beimplemented in hardware, firmware, software, or a combination thereof.For a hardware implementation, all or part of device 102 may beimplemented within one or more application specific integrated circuits(ASICs), digital signal processors (DSPs), digital signal processingdevices (DSPDs), programmable logic devices (PLDs), field programmablegate arrays (FPGAs), processors, controllers, micro-controllers,microprocessors, electronic devices, other electronic units designed toperform the functions described herein, or a combination thereof.

For a firmware and/or software implementation, the methodologies may,for example, be implemented with modules (e.g., procedures, functions,and so on) that perform the functions described herein. Any machine orcomputer readable medium tangibly embodying instructions may be used inimplementing the methodologies described herein. For example, softwarecodes or instructions and other data may be stored in memory, forexample memory 306, and executed by processing unit 304 or other likecircuits within device 102.

As used herein the term “memory” refers to any type of long term, shortterm, volatile, nonvolatile, or other memory and is not to be limited toany particular type of memory or number of memories, or type of mediaupon which information may be stored.

In certain exemplary implementations, the functions described herein maybe implemented in hardware, software, firmware, or any combinationthereof. If implemented in software, the functions may be stored on ortransmitted over as one or more instructions or code on acomputer-readable medium (e.g., 360). Computer-readable media includesboth computer storage media and communication media including any mediumthat facilitates transfer of a computer program from one place toanother. A storage media may be any available media that can be accessedby a computer. By way of example, and not limitation, suchcomputer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or otheroptical disk storage, magnetic disk storage or other magnetic storagedevices, or any other medium that can be used to carry or store desiredprogram code in the form of instructions or data structures and that canbe accessed by a computer. Also, any connection is properly termed acomputer-readable medium. For example, if the software is transmittedfrom a website, server, or other remote source using a coaxial cable,fiber optic cable, twisted pair, digital subscriber line (DSL), orwireless technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or wirelesstechnologies such as infrared, radio, and microwave are included in thedefinition of medium. Disk and disc, as used herein, includes compactdisc (CD), laser disc, optical disc, digital versatile disc (DVD),floppy disk and blu-ray disc where disks usually reproduce datamagnetically, while discs reproduce data optically with lasers.Combinations of the above should also be included within the scope ofcomputer-readable medium.

While certain exemplary techniques have been described and shown hereinusing various methods and systems, it should be understood by thoseskilled in the art that various other modifications may be made, andequivalents may be substituted, without departing from claimed subjectmatter. Additionally, many modifications may be made to adapt aparticular situation to the teachings of claimed subject matter withoutdeparting from the central concept described herein. Therefore, it isintended that claimed subject matter not be limited to the particularexamples disclosed, but that such claimed subject matter may alsoinclude all implementations falling within the scope of the appendedclaims, and equivalents thereof.

What is claimed is:
 1. A method for use in determining a position of amobile device, the method comprising, at the mobile device: acquiring,using a radio-frequency (RF) receiver of a position locating circuitryof the mobile device and during a first mode of operation of theposition locating circuitry, satellite positioning signals at aparticular rate, wherein the satellite positioning signals aretransmitted by a plurality of space vehicles; tracking the plurality ofspace vehicles based on the satellite positioning signals acquiredduring the first mode of operation; determining, respectively, ameasured signal strength value for each one of the plurality of spacevehicles being tracked based on the satellite positioning signalsacquired during the first mode of operation; in response to determiningthat the respective measured signal strength value for each one of thespace vehicles being tracked is at least a threshold signal strengthvalue, initiating a change from the first mode of operation of theposition locating circuitry to a second mode of operation of theposition locating circuitry; and acquiring, using the RF receiver andduring the second mode of operation, signals from one or more of theplurality of space vehicles at a rate less often than that of the firstmode of operation.
 2. The method of claim 1, wherein, while theoperational mode of the position locating circuitry of the mobile devicecomprises the second mode, the position locating circuitry is configuredto not attempt to reacquire satellite positioning signals from theplurality of space vehicles during a period of a duty cycle.
 3. Themethod of claim 1, wherein initiating the change from the first mode ofoperation of the position locating circuitry to the second mode ofoperation is further based, at least in part, on determination that anumber of the plurality of space vehicles being tracked exceeds athreshold number.
 4. The method of claim 1, wherein initiating thechange from the first mode of operation of the position locatingcircuitry to the second mode of operation is further based, at least inpart, on determination that corresponding position information for eachof the plurality of space vehicles being tracked is accessible to themobile device.
 5. The method of claim 1, wherein initiating the changefrom the first mode of operation of the position locating circuitry tothe second mode of operation is further based, at least in part, ondetermination that position information corresponding to any of theplurality of space vehicles being tracked is not currently beingreceived.
 6. The method of claim 1, wherein initiating the change fromthe first mode of operation of the position locating circuitry to thesecond mode of operation is further based, at least in part, ondetermination that an error associated with a current positiondetermined based, at least in part, on at least a portion of thesatellite positioning signals acquired from the plurality of spacevehicles does not exceed a position error threshold.
 7. The method ofclaim 1, and further comprising, at the mobile device: subsequent toinitiating the change from the first mode of operation of the positionlocating circuitry to a second mode of operation, initiating a furtherchange from the second mode of operation of the position locatingcircuitry to the first mode of operation based at least in part on atimed condition corresponding to the change from the first mode ofoperation of the position locating circuitry to the second mode ofoperation.
 8. A mobile device comprising: position locating circuitryconfigured to: acquire, using a radio-frequency (RF) receiver of theposition locating circuitry and during a first mode of operation,satellite positioning signals at a particular rate, wherein thesatellite positioning signals are transmitted by a plurality of spacevehicles; track the plurality of space vehicles based on the satellitepositioning signals acquired during the first mode of operation; anddetermine, respectively, a measured signal strength value for each oneof the plurality of space vehicles being tracked based on the satellitepositioning signals acquired during the first mode of operation; and acontroller coupled to the position locating circuitry and configured to:in response to determining that the respective measured signal strengthvalue for each one of the space vehicles being tracked is at least athreshold signal strength value, initiate a change in the positionlocation circuitry from the first mode of operation to a second mode ofoperation, wherein the position locating circuitry is further configuredto acquire, using the RF receiver and during the second mode ofoperation, signals from one or more of the plurality of space vehiclesat a rate less often than that of the first mode of operation.
 9. Themobile device of claim 8, wherein, while the operational mode of theposition locating circuitry comprises the second mode, the positionlocating circuitry is configured to not attempt to reacquire satellitepositioning signals from the plurality of space vehicles during a periodof a duty cycle.
 10. The mobile device of claim 8, wherein thecontroller is configured to initiate the change from the first mode ofoperation to the second mode of operation further based, at least inpart, on determination that a number of the plurality of space vehiclesbeing tracked exceeds a threshold number.
 11. The mobile device of claim8, wherein the controller is configured to initiate the change from thefirst mode of operation to the second mode of operation further based,at least in part, on determination that corresponding positioninformation for each of the plurality of space vehicles being tracked isaccessible to the mobile device.
 12. The mobile device of claim 8,wherein the controller is configured to initiate the change from thefirst mode of operation to the second mode of operation further based,at least in part, on determination that position informationcorresponding to any of the plurality of space vehicles being tracked isnot currently being received.
 13. The mobile device of claim 8, whereinthe controller is configured to initiate the change from the first modeof operation to the second mode of operation further based, at least inpart, on determination that an error associated with a current positionlocation determined based, at least in part, on at least a portion ofthe satellite positioning signals acquired from the plurality of spacevehicles does not exceed a position error threshold.
 14. The mobiledevice of claim 8, wherein the controller is configured to subsequentlyinitiate a further change of the position locating circuitry from thesecond mode of operation to the first mode of operation based at leastin part on a timed condition corresponding to the initiated change fromthe first mode of operation to the second mode of operation.
 15. Anapparatus for use in determining a position of a mobile device, theapparatus comprising: means for acquiring, during a first mode ofoperation of the apparatus, satellite positioning signals at aparticular rate, wherein the satellite positioning signals aretransmitted by a plurality of space vehicles; means for tracking theplurality of space vehicles based on the satellite positioning signalsacquired during the first mode of operation; means for determining,respectively, a measured signal strength value for each one of theplurality of space vehicles being tracked based on the satellitepositioning signals acquired during the first mode of operation; meansfor determining that the respective measured signal strength value foreach one of the space vehicles being tracked is at least a thresholdsignal strength value; means for initiating a change from the first modeof operation of the apparatus to a second mode of operation of theapparatus in response to a determination that the respective measuredsignal strength value for each one of the space vehicles being trackedis at least the threshold signal strength value; and means foracquiring, during the second mode of operation, signals from one or moreof the plurality of space vehicles at a rate less often than that of thefirst mode of operation.
 16. The apparatus of claim 15, wherein themeans for initiating the change from the first mode of operation of theapparatus to the second mode of operation is configured to initiate thechange from the first mode of operation to the second mode of operationbased, at least in part, on: (a) a determination that a number of theplurality of space vehicles being tracked exceeds a threshold number; or(b) a determination that corresponding position information for each ofthe plurality of space vehicles being tracked is accessible to themobile device; or (c) a determination that position informationcorresponding to any of the plurality of space vehicles being tracked isnot currently being received; or (d) a determination that an errorassociated with a current position location determined based, at leastin part, on at least a portion of the satellite positioning signalsacquired from the plurality of space vehicles does not exceed a positionlocation error threshold; or (e) some combination of (a), (b), (c), or(d).
 17. The apparatus of claim 15, and further comprising means forsubsequently initiating a change from the second mode of operation ofthe apparatus back to the first mode of operation, based at least inpart on a timed condition.
 18. A computer-readable non-transitorystorage medium having computer implementable instructions stored thereonthat are executable by one or more processing units of a mobile deviceto: acquire, during a first mode of operation of the mobile device,satellite positioning signals at a particular rate, wherein thesatellite positioning signals are transmitted by a plurality of spacevehicles; track the plurality of space vehicles based on the satellitepositioning signals acquired during the first mode of operation;determine, respectively, a measured signal strength value for each oneof the plurality of space vehicles being tracked based on the satellitepositioning signals acquired during the first mode of operation;determine that the respective measured signal strength value for eachone of the space vehicles being tracked is at least a threshold signalstrength value; and initiate a change from the first mode of operationof the mobile device to a second mode of operation of the mobile devicein response to determining that the respective measured signal strengthvalue for each one of the space vehicles being tracked is at least thethreshold signal strength value; and acquire, during the second mode ofoperation, signals from one or more of the plurality of space vehiclesat a rate less often than that of the first mode of operation.
 19. Thecomputer-readable non-transitory storage medium of claim 18, wherein thecomputer implementable instructions stored are further executable by theone or more processing units of a mobile device to initiate the changefrom the first mode of operation of the mobile device to the second modeof operation further based, at least in part, on: (a) a determinationthat a number of the plurality of space vehicles being tracked exceeds athreshold number; or (b) a determination that corresponding positioninformation for each of the plurality of space vehicles being tracked isaccessible to the mobile device; or (c) a determination that positioninformation corresponding to any of the plurality of space vehiclesbeing tracked is not currently being received; or (d) a determinationthat an error associated with a current position location determinedbased, at least in part, on at least a portion of the satellitepositioning signals acquired from the plurality of space vehicles doesnot exceed a position location error threshold; or (e) some combinationof (a), (b), (c), or (d).
 20. The apparatus of claim 18, wherein thecomputer implementable instructions stored are further executable by theone or more processing units of a mobile device to subsequently initiatea change from the second mode of operation of the mobile device back tothe first mode of operation, based at least in part on a timedcondition.